This invention relates to an apparatus for disassembling a wooden article and is especially adapted for disassembling wooden pallets in order to replace broken boards. More particularly, the invention concerns an apparatus that is capable of breaking the nails between the slats and a supporting stringer on both sides of the stringer during a single pass through the apparatus.
U.S. Pat. No. 3,869,780 to Ginnow et al for an UNNAILER discloses a practical apparatus for disassembling wooden pallets and includes a pair of free-rotating circular blades carried by an elongated support arm mounted at one end of a frame. A pallet is moved relative to the circular blades to effect cutting of the nails by the relative movement between the pallet and the blades. The support arms are side-by-side horizontal cantilevered arms. The complicated, failure-prone means for aligning the interface between the pallet slats and stringer in the Ginnow et al patent was replaced in subsequent designs by self-aligning means for aligning the cutting blades with the interface.
Because the Ginnow et al apparatus cuts the nails on one side of a stringer, six passes were required to completely disassemble a pallet. In Williams U.S. Pat. No. 4,320,570 and 4,435,892 for an apparatus and method of disassembling wooden pallets, three sets of side-by-side support arms and rotary cutting blades are positioned to simultaneously cut the nails on one side of three pallet stringers such that only two passes are required to disassemble a pallet. The Williams method and apparatus has met with limited success because of the complexity involved including the necessity for providing lateral adjustability to the support arms.
Other techniques, that deviate from the general approach suggested in the Ginnow et al patent, have been suggested in the prior art. For example, U.S. Pat. No. 4,241,495 issued to Wakeem for a METHOD AND APPARATUS FOR DISASSEMBLING WOODEN PALLETS, discloses three pair of motor-driven rotary cutters that are vertically applied to an on-end pallet. Each set of cutters includes positioning fingers for contacting the inner surface of the slats to guide the driven cutters into the space between the slats in the stringer. This patent not only requires lateral adjustment of the cutting heads to match the stringers, but provides motor-driven cutters with adjustable-length drive shafts to accommodate various stringer widths. Such complexities, which increase down-time, thwart the very goal of the design, which is to increase productivity.
In addition to difficulties in achieving increased productivity, other deficiencies in the basic Ginnow device remain. The cutting blades, which are an expensive item and require substantial machine down-time to replace, are prone to a catastrophic failure mode in which the severe stress of cutting hardened nails causes the blade to sever laterally into two or more pieces. In addition, the necessity of moving a pallet sufficiently forward across the blades in order to sever the nails for each slat, requires that a portion of the pallet-moving mechanism come perilously close to the blades, resulting in occasional metal-to-metal contact, which further damages the blades. Thus, the need exists for a pallet disassembler which provides enhanced productivity while improving reliability and durability.